I just don't get it..

I'm editing a fairly large MS Word document, into which I've inserted about 20 graphics and photos. The complete file size started at around 100KB, increased as I inserted pictures, and then continued to increase as I edited the document, shifted text and images around, and resaved. At one point, it was up to 2MB, then suddenly dropped to around 400K where it belonged. It then started increasing again, and a moment ago it was up to almost 10MB--but it just dropped to 644KB with the latest save. I don't get it.. it seems arbitrary.
Of course, I'll be saving it as PDF in the long run, so it doesn't really matter.. just odd behavior.

Update: My dad explained it! Word automatically saves lots of prior versions (Undo steps, basically) in the current copy of the file, which increases the file size significantly if there are pictures involved. This is rectified when you quit Word, or enough time passes to clear the cache of large Undo steps. :)

Evening!

Lemon-mustard chicken, twice-baked potatoes, an overly-long phone call to the parents (not bad, just long) and now (most likely) watching Jurassic Park again. :)

Also, surprisingly, campus store had both rolls of pictures developed--including the one I dropped off yesterday! I was pleased. :) So, sooner or later, you'll all get to see oodles of pictures of Peanut and Valkyrie, mostly. And some other stuff. :)